Having no other work than 'gunk' to describe what fell on their homes and vehicles, residents of Macomb County in southeast Michigan are baffled by the black substance that rained down from the sky.

According to The Macomb Daily,

Residents of a Harrison Township neighborhood received a surprise from above Sunday when they discovered a black, oily, substance splashed on their roofs, vehicles and driveways.

And the source of the substance, along with its makeup, are so far a mystery.

WXYZ TV in Detroit visited the affected homes, which is located near Selfridge Air Base, and speculated that the mystery gunk may have come from aircraft.